DIFFERENTIAL EXPRESSION ANALYSIS OF BORON TRANSPORTERS AND SOME STRESS-RELATED GENES IN RESPONSE TO 24-EPIBRASSINOLIDE AND BORON BY SEMI-QUANTITATIVE RT-PCR IN Arabidopsis thaliana (L.) Heynh

Plant steroidal hormones, brassinosteroids (BRs), promote plant developmental processes and enhance tolerance to several abiotic stresses including high boron (B) stress. To examine the possible role of BR in high B-induced stress at the transcriptional level, we investigated the response of B transporter genes (BOR1-4), high B-induced genes (MATE, Hsp-like), BR-induced genes (Hsp70-4, Hsp90-1) and other stress-related genes (LTI/COR78, LEA4-5) upon exogenous treatments of 24-epibrassinolide (EBL) on Arabidopsis thaliana (L.) Heynh exposed to high concentrations of boric acid (BA) using semi-quantitative RT-PCR. BA treatments led to down regulation of BOR1 and BOR3 genes in leaf and root tissues and higher concentration of EBL further decreased expression of these genes in roots. The expression of high B-induced genes was observed to be upregulated by 1 mu M EBL treatment under high B stress in both tissues of the seedlings. The upregulation of BR-induced genes were clearly evident in root tissues co-treated with 1 mu M EBL and BA as compared to BA alone. Higher concentration of EBL was found to be more effective in increasing expression of LTI/COR78 gene in root and LEA4-5 gene in shoot tissues. To our knowledge, this is the first report how exogenous application of EBL modulates high B stress responses at molecular level in model plant Arabidopsis thaliana.